There has been an increasing requirement to provide digital to analog converters with increasing resolution. As a result, 16 bit digital to analog converters are now commercially available at relatively inexpensive prices. Simultaneously there remains a desire to reduce the component count within a circuit and this has resulted in multi-channel digital to analog converters becoming popular. Placing multiple digital to analog converters within a single chip is relatively simple to do whilst the resolution of the converter remains relatively low, for example 8 bits. However as the resolution of the converter is increased problems such as accurately defining a ground voltage can arise. Normally a multi-chip digital to analog converter produces multiple outputs with voltages with respect to a single “ground” reference. However the circuits being driven by the outputs of the digital to analog converter may not be tightly grouped together on the circuit board and, as a consequence, each circuit may experience a slightly different “ground” voltage due, for example, to current flow through the conductors defining the ground path. Thus, whilst the ground voltages of various circuits may approximately the same, they may not be exactly at the same voltage as a “reference ground” voltage experienced at the digital to analog converter. To put this in perspective, if a 16 bit digital to analog converter has an output range spanning between zero and 10 volts then the size of one least significant bit (LSB) is only 150 μV. For a device having an output between −10 and +10 volts the LSB would become 300 μv. It can be seen that current flows occurring within the conductors defining the ground voltage could easily give rise to voltage drops significantly greater than 150 μV, and in some situations the local ground voltage at a device receiving an output from the DAC could differ from the local ground voltage at the DAC by the equivalent of 100 or so least significant bits. Thus the use of an assumed ground voltage occurring in each circuit driven by the multi-channel digital to analog converter is incorrect and may significantly degrade the performance of the circuit away from its nominal 16 bit resolution and associated accuracy.